Optical projection apparatus



Jan. 29, 1935.

C. F.HITCH|NS ET Al, OPTICAL PROJECTION APPARATUS 1933 3 Sheets-Sheet l Filed May 11 i C W. 6 @errar/ 3 Sheets-Sheet 2 Jan. 29, 1935. c. F. HITcHlNs l-:r A1.

OPTICAL PROJFLCTION APPARATUS Filed May 11, 1935' www Jan. 29, 1935.` A c. F. HlTcHlNs ET AL.

OPTICAL PROJECTION APPARATUS Filed May l1, 1955 3 Sheets-Sheet 5 Patented Jan. 29, 1935 OPTICAL rRoJEc'rIoN APPARATUS Charles Faunce Htchins and Charles v`William f Godley Gerrard, Westminster;b London, Eng` land, assignors, by' direct andmesneassigm. ments, of one-tenth to Sky Publicity Limited, London, England, and nine-tenths to William 'Francis Eggintn'Briggs, London, England y Application Mayl 11, 1933,- seial Nol 67'0,5s4 InGreat Britain October 11, 1932 s claims'. (ci. sri-.gn

AThe invention'relates to .optical projection apparatus, and though not restricted to such ap- --plication, -is especially suitable for optical pro- "jecting on the c1ouds,-ior advertising or other pulpOSeS.

` l In some cases;l it is 'desirable to project a clock 'face on the clouds or the like, and the 'present invention seeks ,toV` overcome Vvdii'iculties due to `the great vheat concentrated at the focus of the Vvprojecting-mirror, where the clock face is situated. I

. With such a main object, the invention consists inthe combinations of elements hereinafter delscribedand particularly pointed outin the claims.

Referring to the accompanying drawings which are of a diagrammatic naturez VFigure 1 shows a general view partly asa sectional elevationfof one form of apparatus'towhich the invention is applicable;

Figure2 is a sectional elevation to an scale of a clock, while Figure 3 is a corresponding elevation.

The general features of one form of projector, suitable for sky projection, to which the present invention is applicable comprise (see Figure 1) an elongated casing, 2, mounted on trunnions, 3, about which it can be turned to different altitudes by a gear wheel, 4, meshing with a toothed sector, 5. The projector can also be moved in azimuth by help of the hand-wheel, 6, actuating the toothed pinion, 7, gearing with the fixed gear wheel, 8.

The projector is provided with an ellipsoidal mirror, 9, in the proximate focus of which the crater carbon, 10, of an arc lamp, 11, is arranged, products of combustion from the arc being withdrawn from the casing by means of a suction fan, 12. l

The object, 13, to be projected, and in some cases made of or depicted on quartz or other refractory material, is arranged in the conjugate focus of the mirror, whence the rays of light pass on through the adjustable lens system, 14.

Since heat in addition to light is concentrated at the focus, the object, 13, and lens system, 14, may be cooled, if desired, by air from a fan, 15, driven for example by an electric motor.

According to one form of the present invention, a plate or screen, 16, of carborundum, firebrick or other suitable opaque and refractory material is disposed between the mirror, 9, and the clock face, the plate having a circular hole, 17, for example, three inches in diameter, to dene the illuminated area in the focus of the mirror. The numerals, 18, for example of platinum,

enlarged strips, 19, of, for example, platinum, 'running';out

' of; the clock facevare situated Yjust withinv this k"illuminatedarea, and are Asecured in place by wardly, and 4clamped between two"V supporting Y platesf 20, 21, which are held stationary in a,..=:

plate, 22, forming the clock. v

This supporting framework may be: positioned in the casing, 2, of the projector inany suitable manneiyone particular method being referred tomore in .detail-hereinafter.l n n I, j

On one vside of these supporting plates, 20,21, a metal ring, 23, toothed-at 24'round its periphery, is arranged to run in balkbe'arings,v 25, betweenfthe supporting plate, 20,` and an outer'annulus 28d, 'of L-shaped crosssection," this"-ring, 23, carrying aplate, 2 6, of a refractory material such as vquartz-,fonwhich thefhourilandy-Z'l, ofv the block is carried or depicted; for example, the hand may be of sheet platinum contoured to the shape desired, or a representation of the hand may be painted on the plate.

On the other side of the supporting plates, 20, 21, the minute hand, 28, of the clock is carried by a similarly mounted rotatable toothed ring, 29, disposed between the supporting plate, 21, and annulus, 21a, of L-shaped cross-section, the hand projecting inwards, and being carried, it may be, by a radially running strip, 30, of platinum (see particularly Figure 3) secured to the ring, 29.

Finally, the supporting plates, 20, 21, and the Ll-shaped annuli, 20a, 21a, with base members butting thereagainst to leave intervening spaces for the accommodation of the rings, 23, 29, are secured together by bolts, 2lb, as shown in detail in Figure 2.

In order to drive the hands, suitable clockwork (not shown) enclosed in a casing, 31, is arranged outside the beam of light from'the mirror, 9, the clockwork actuating two co-axial toothed wheels, 32, 33, gearing respectively with the toothed rings, 23, 29, above described, and preferably of the same size, the spindle, 34, of the wheel, 32, passing through the hollow spindle, 35, of the wheel, 33. l

In this way it will be seen that, while the driving mechanism, hands and dial of the clock form a single self-contained unit, only the hands, 27,

the supporting framework of 28, and the numerals, 12, are within the projecting beam of light, the supporting plate, 22, toothed rings, 23, 29, and driving mechanism being outside the beam, and protected from heat at least in part by the carborundum or like plate, 16.

In some cases, cold air from the fan, 12, may be blown into the casing, 31, surrounding the clockwork, and/or the clockwork may be enclosed in a heat-insulating casing constructed on the thermos-flask principle.

A carrier, such as 36, (see Figure l) is provided having aenumber ,of Kobjects to be projected arrangedsround :its periphery; .this icarrier,;:36, l,is

movably mounted, for example, about a centre,

so that any of a number of objects can beiexplates and means for clamping said juxtaposed posed, the objects being remoyiab-lesdesired'so that they can be exchanged ior'others,

The clock face and handsabovetdescribed,and

its driving mechanism arearrangedtoibeirnounte,4 ed as a detachable unit on thecarrier;gandto" be retained therein by suitable `clips,f'forflfthe like. Y

tion, the driving mechanismgxmaygbefomitted and the clock-hands set by hand; enig; inthemase of the rotary carrier, 36, the hands o f ,theolook may be set, by help of a door in the carrierY casing,

its .lewestfpostion so that .when `the Clock -S giarlriedround ,into,thefprojectingbeam, ,it'frwill' be `'ire,sistfffrine...the correct time.

-Jsymbolssuchgas letters, supported fa similar manner, so that advertisements, noticesfor the :,likefhmay'be-projected. A l v :ln-,somecases to f facilitate this operation, the

numerals y51.8, above V,described ,with their eupporting strips, 19,` ,if-any, .may be, provided krwith bases having say, ,a.p,a ir yof .holes for,,registration purposes, which basescanibeplacedovergprojecting pinsland ,.clamped.-inplace.

Havingfnow described -our-invention, what -we rglamsas newandidesire `vtog'secure by LettersPatf` l1.. A-.\l0. zkf,tace for critical ,prqiection purposes :formationat `a radius less than said certain ra- `iius, outwardly extending means for supporting Said:Symbols,:saidfsupporting means passing be- Ltweenesaidjuxtaposed plates, annuli of L-shaped According to an alternative.'method-fv pril- -rneans and prevent their optical projection.

comprising, in combination, a pair of juxtaposed plates through a central area in which light can pass, a plurality of clock-face hour-indicating symbols disposed in ring formation within said central area, means for supporting said symbols and extending-outwardly therefrom, said supporting means passing between said juxtaposed .,platesfltogether.

2. A clock face for optical projection purposes comprising, combination, a pair of annular `plates juxtaposed `and having apertures there- 4'throughfiofa certain radius, a plurality of clockface y lignir-findicating symbols disposed in ring cross-,section disposed on opposite sides of said juxtaposed plates, rotatably-mounted means for `,ckzarrying respectively -the hour handr andfthe minute hand ldisposed between saidv rjuxttfPQSfd K plates and said annuli,` together v,with means; tor -..Thenumerals, lyimay-.be readily'lremovedJf A 25 mdesired,andireplaced,individually :bv ,designs .or

clamping said juxtaposedfplates, said symbolsupporting means and said annuli together; x3. Afclock face-fortopticalprojectionpurfposes ...comprising ;in koo mbination agplurality ,of hourindicating :symbols yand means for' Supporting said symbols ,in ring formation,-ashieldoheat-resist- `material having a circularf'aperturetherein Q30 and disposed on the light-receiving side Y0f ,-jSaid 11mg 0f symbols, said circular aperture-having .a diameter Aabout equal to the outside diameter ,oflsaid v ring of symbols to screen said :supporting ,CHARLESFAUNCE HITCHINS. v 'Y Y ,CHARLES WILLIAM ,GODLEY GERRA'RD; 

